It is generally a good idea to also replace the stem when replacing a crown for a couple of reasons. The stem may be rusty or when removing the crown the stem will snap off. They are not expensive usually so I will attempt to explain how to do a crown replacement with an old stem. The new stem procedure is different as the stem will come longer than desired and will need to be filed to the correct size.
Removing the old crown as I stated can be a problem. A pin vise and a plier are the tools necessary to start. Grip the stem near the crown with the vise. Gently turn the crown first with your fingers to see if it will unthread. If not, gently with a plier. If it still is a problem some heat may help to loosen the thread lock used on the stem when it was originally installed. Very little heat should be necessary.
Once removed from the crown, clean dirt and rust from the threads. Apply new thread lock, a tiny amount is all that is necessary, and insert in crown and tighten. Doesn't have to be "torqued' just snug. I use my fingers to tighten. The thread lock will keep it in place.
Now the difficult part for the uninitiated. Determining if the new stem and crown assembly is the correct length to operate the watch properly and also provide the water resistance as designed.
There are lots of variables but in general you want the crown to "almost" touching the case. You also want the stem to operate the watch properly, move from the first click to the second and back to the operating position. If the new assembly is shorter than the original, the watch may not work properly.
A screw down crown is a whole different ball game and a new stem as well as crown is more involved. First timers may be able to do this if everything goes right. The difficult part is repairing or adusting when everything doesn't go right.
Michael, Wostep
